The present invention relates to an optical recording medium of write once type and a method for setting power of a laser beam for writing information in the recording medium.
As a write once type optical recording medium, a CD-R (write once type CD) is known. In the CD-R, a laser beam is focused on a recording surface to convert luminous energy to thermal energy to change the physical nature of the recording surface. Thus, the information is recorded n the CD-R.
Although the recording mediums of the same type are made by the same material, the individual recording medium has not always the same characteristic. Accordingly, if a laser beam is set to a fixed power, information can not be recorded in an optimum condition. Therefore, in such a recording medium, before recording information, the laser power is adjusted by an optimum power control (OPC) to be set to an optimum value for a disc to be recorded.
A conventional OPC method employed in the CD-R will be describe with reference to FIG. 6. The CD-R has a power calibration area (PCA) as a test area, read-in area, information recording area, and read-out area. The PCA is provided on the inside of the read-in area. A test writing is performed in the test area before recording information so as to obtain an optimum laser power for writing information on the CD-R.
In the write once type CD such as the CD-R, an area in which information has been written once is not used for further writing information again. A recorder for writing information is provided for controlling laser power by the test writing on the PCA, and for recording information on the information recording area thereafter with the controlled laser power.
As shown in FIG. 6, the CPA is divided into a hundred partitions. Since one writing test uses one partition, it is possible to perform a hundred times of the OPC.
However, the test writing over a hundred times can not be done. Therefore, even if a writable area (vacant space) remains in the information recording area, information can not be recorded thereon.
An object of the present invention is to provide an optical recording medium of a write once type and a method for setting power of laser beam for writing information in the recording medium in which the number of writing tests is increased as many as possible.
According to the present invention, there is provided an optical recording medium on which information is recorded in an information recording area by changing a physical quality thereof, comprising a plurality test areas on each of which test signals are written for obtaining an optimum laser power for writing information on the information recording area, a plurality of power setting information recording areas on each of which an optimum laser power obtained by reading the recorded test signal written in one of the test areas, and an identification information of a recording system by which the test signal is written are written.
A method of the present invention comprising steps of writing test signals on test areas, obtaining an optimum laser power for writing information on an information recording area, writing an optimum laser power obtained by reading the recorded test signal written in one of the test areas, and an identification information of a recording system by which the test signal is written on a power setting information recording area, reading out an own identification information of the recording system recorded on the power setting information recording area, reading out an optimum laser power written in the power setting information recording area in which the own identification information is written, setting power of laser beam for recording information to the read out optimum laser power.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.